Talk:Instrumental temperature record

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Old general discussion[edit]

I've (William M. Connolley 20:03 Feb 12, 2003 (UTC)) moved 2 paras to the end. These are:

the intro that someone copied in, viz:

"The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history. Climate scientists generally agree that Earth has undergone several cycles of global warming and global cooling in the last 20,000 years, with the average air temparature fluctuating within a range of about 3 Celsius degrees (5 Fahrenheit degrees), over this time period."

This is mangled info. Someone can straighten it out if they like. If you look over the last 20 kyr, the biggest signal you see is the end of the last ice age - so the stuff about little cycles is then in the noise.

There are various sub-cycles/sub-signals, of ??1500 year ish?? periodicity; and their are the D-O events etc etc. But the above para mangles that. *Also* it fits rather poorly with the emphasis of this subsection-now-a-page, ie on the last 150 or 1000 years - so it shouldn't be up there in the intro.

I've also pushed

"In January 2002, scientists released data showing that Antarctica had grown about 25% (???). Some editorial writers claimed that this contradicts the expectation that rising temperatures should cause the ice cap to shrink. However, the scientists studying the situation in the Antarctic who released this data point out that local cooling in some areas is consistent with an overall trend of global warming and say that "the ice-sheet growth that we have documented in our study area has absolutely nothing to do with any recent climate trends."[9]"

into the misc section. The first sentence is junk. If its to stay, someone has to find a decent ref to what its supposed to mean. Mind you, ref [9] is nice and its a pity I've misc'd it too...

The IPCC says that it has corrected the land station data to account for the urban heat island effect. To do: find and summarize their correction technique.

The comment above has been around for about a year, and still no one has shown me where in any IPCC report they have explained how they "account for" urban heat islands. So I'm inclined to say rather:

Critics of the IPCC report note that it fails to explain how it accounts for the urban heat islands. These critics argue that the heat island effect correlates with land-based thermometer readings better than the global warming theory espoused by the IPCC.

... or something along those lines. Work with me here, folks. Let's make an informative and neutral article. --Uncle Ed

That looks fairly reasonable - I'd modify slightly:

The IPCC report does not explain how it accounts for the urban heat island effect - increased warming due to proximity to major cities. The heat island effect, if not properly accounted for, would tend to increase the amount of apparant warming.


(William M. Connolley 09:46 Feb 13, 2003 (UTC)) There is at least a problem in the wording here. IPCC doesn't do research, it reports other peoples. But apart from that... see section [1]. In particular:

These results confirm the conclusions of Jones et al. (1990) and Easterling et al. (1997) that urban effects on 20th century globally and hemispherically averaged land air temperature time-series do not exceed about 0.05°C over the period 1900 to 1990 (assumed here to represent one standard error in the assessed non-urban trends). However, greater urbanisation influences in future cannot be discounted. Note that changes in borehole temperatures (Section 2.3.2), the recession of the glaciers (Section, and changes in marine temperature (Section, which are not subject to urbanisation, agree well with the instrumental estimates of surface warming over the last century. Reviews of the homogeneity and construction of current surface air temperature databases appear in Peterson et al. (1998b) and Jones et al. (1999a). The latter shows that global temperature anomalies can be converted into absolute temperature values with only a small extra uncertainty.

Errr... shouldn't all this go into the UHI page?

Yep. And then summarised here. :) It all seems rather a lot of work... :-/ Martin
William, the large quote above (0.05°C over the period 1900 to 1990) seems at first reading to answer Martin's other question: are heat islands causing global warming. My question is different: are temperature readings taken within heat islands giving a false impression of global warming. That is, (1) if a city gets 0.8°C warmer, and this warming is averaged in with all other temperature differences, I think this would be a statistical error. What do you think? Also, (2) if cities get much warmer, suburbs get kind of warmer, rural areas get a bit warmer, and uninhabited areas don't get warmer at all, what would this tell us? (Not saying that's the case for now, just asking what this would tell us if it were so.) --Uncle Ed 17:19 Feb 13, 2003 (UTC)
AFAICT, "globally and hemispherically averaged land air temperature time-series" - I think this phrase is referring to the temperature readings rather than the actual temperatures - IE, it answers your question... Oh, I'm copying some of this stuff to the urban heat island page. Martin
There is an answer to UE from IPCC. Essentially, you can (if you wish) separate out the obviously-likely-to-be-affected stations if you like, but it makes little difference. Reasons include: cities are small areas anyway; the trends from cities (etc) don't in fact differ substantially from the trends without them; in fact the trends over city areas agree quite well with the dreaded MSU... I'll try to find this and add it in, since its clearly a concern (William M. Connolley 21:31 Feb 13, 2003 (UTC)).

I have started studying a paper on the temperature record in the USSR. The writers find no warming trend in rural stations and hint (or imply) that other researchers have selectively chosen data to fit their "warming" views. [Read it yourself] and decide. --Uncle Ed 17:52 Feb 13, 2003 (UTC)

Its worth reading (William M. Connolley 21:36 Feb 13, 2003 (UTC)). I've had a brief look before. Of the 2 stations I picked to check his analysis, one had the jump he claimed (according to objective statistics) and one didn't, or it was impossible to tell: the trends he claimed as implausible against "neighbouring" stations were from places 100's of km away, and in different exposures: near the sea or not.

Martin and William,

I'm not sure either of you is getting my point. I am not wondering whether a few hot cities are making the whole world hot.

I am wondering whether a large number of the temperature readings from weather stations in and near rapidly warming cities, when averaged with a relatively small number of temperature readings from rural and remote stations, are giving a false impression of global warming. That is, it might be that (A) the only parts of the world that are warming are the urban heat islands and (B) the only reason these are heating up is because cities absorb and generate heat; rather than (C) that carbon dioxide, etc. is causing worldwide warming.

Do you understand my point? (I'm not asking whether you agree with my point of view, but only whether my English is clear.) --Uncle Ed 22:33 Feb 13, 2003 (UTC)

I believe so - let me paraphrase to try and prove it.
* Because of the urban heat island effect, cities are warming up more than the surrounding countryside
* Thermometers are recording an increase in temperature
* Many thermometers are located near urban heat islands
* Therefore, the temperature increase recorded by thermometers may overestimate the actual temperature increase of the climate as a whole.
To draw a parallel, one shouldn't put the thermostat in one's house next to a log fire, because in that case the thermostat will overestimate the general temperature of one's house.
My reading of the IPCC report is that the distortion introduced by the urban heat island effect is, at most, 0.05°. In other words, if we had located our thermometers away from urban heat islands, they would have recorded 0.05° less temperature increase over the period 1900 to 1990. Of course, this depends on whether you trust the research cited by the IPCC... Martin
I mostly agree with Martin. Have you read the bit about marine and borehole temperatures? This does a lot to counter your point. I also think you're wrong to suppose that, numerically, urban reading predominate. Martin: note that strictly speaking IPCC reprots that UHI leads to at most 0.05 *uncertainty*. They don't (I think) explicitly state that this is necessarily in the warming direction.

Thank you, both, for helping me to feel understood. Now I'll have a G-R-E-A-T weekend! ^_^ (Uncle Ed)

Temperature anomaly?[edit]

This article uses the phrase "temperature anomaly" a lot. It is used exclusively as the measure of temperature (temperatures are never given in absolute terms, only as "anomaly" degrees). Yet the article never once defines temperature anomaly, or explains what it is with respect to. Nor is there a Wikipedia article on Temperature anomaly. This makes the whole discussion fairly useless. Can a section be added which explains what this is? (I'd add it myself, but I seriously don't know what it means and Google only turns up vague answers.) —MattGiuca (talk) 03:40, 8 November 2011 (UTC)

Repetitive citations[edit]

I'm thinking of changing the IPCC citations in this article. I would change the citations so that they use Template:Harvard citation no brackets as is done in effects of global warming. The change would remove a lot of repetitive information contained in the existing IPCC citations. The change could also be applied to any other citations which contain repetitive information. I'd probably make the changes gradually, perhaps revising a few citations in each edit. Enescot (talk) 05:12, 20 November 2012 (UTC)

Scientific background section[edit]

I took this out again [2]. Sorry, but the entire thing seems far too Hansen-centric. It might be suitable for NASA's website, but not here. Also, the refs-in-front-of-each-para is ugly, but thats comparatively minor William M. Connolley (talk) 09:16, 30 November 2012 (UTC)

While I agree that my edit was less-than-ideal, I still think that it contained some useful information. As I'm sure you're aware, several issues are important to the analysis of global temperature, e.g., the correlation of anomalies across large areas, and why temperature anomalies are used in preference to absolute temperatures (see also the "Temperature anomaly?" thread above). Perhaps you could take a look at this other NASA public-domain source: [3]. In my opinion, some of its content could be adapted for use in this article. Its focuses on the NASA temperature analysis, but I still feel that it may be of some use. Enescot (talk) 05:27, 5 December 2012 (UTC)
Indented below, I've pasted some public-domain content that I would to add to this article. The text below is not a draft, and would need to be rewritten before it is added to the article::
"Our analysis concerns only temperature anomalies, not absolute temperature. Temperature anomalies are computed relative to the base period 1951-1980. The reason to work with anomalies, rather than absolute temperature is that absolute temperature varies markedly in short distances, while monthly or annual temperature anomalies are representative of a much larger region. Indeed, we have shown (Hansen and Lebedeff, 1987) that temperature anomalies are strongly correlated out to distances of the order of 1000 km" [4]
"Q. What do I do if I need absolute SATs, not anomalies ? A. In 99.9% of the cases you'll find that anomalies are exactly what you need, not absolute temperatures. In the remaining cases, you have to pick one of the available climatologies and add the anomalies (with respect to the proper base period) to it. For the global mean, the most trusted models produce a value of roughly 14°C, i.e. 57.2°F, but it may easily be anywhere between 56 and 58°F and regionally, let alone locally, the situation is even worse." [5]
Enescot (talk) 05:05, 18 December 2012 (UTC)
I agree, the "Calculating the global temperature" deserves expansion. Use of anomalies, and correlation-lengthscale, are important points that should be mentioned. Incidentally I think the "freeware" bit should be revised - jvv's is (I think) dead but (again, I think) GISS now use the python version from CCC William M. Connolley (talk) 09:10, 18 December 2012 (UTC)
I've put together a draft revision of the "Calculating the global temperature" section. I suggest that the"Calculating the global temperature" section is moved up the article so that it is below the "Global records databases" section. The concept of temperature anomalies is used throughout the article, and I think that it is worth explaining near the top of the article.
"(existing text)...In the late 1990s, the Goddard team used the same data to produce a global map of temperature anomalies to illustrate the difference between the current temperature and average temperatures prior to 1950 across every part of the globe.[35]
(new section) Absolute temperatures versus anomalies
Records of global average surface temperature are usually presented as anomalies rather than as absolute temperatures. A temperature anomaly is measured against a reference value. For example, if the reference value is 15 °C, and the measured temperature is 17 °C, then the temperature anomaly is +2 °C (i.e., 17 -15).
Temperature anomalies are useful for deriving average surface temperatures because they tend to be highly correlated over large distances (of the order of 1000 km). In other words, anomalies are representative of temperatures over large areas and distances. By comparison, absolute temperatures vary markedly over even short distances.
Absolute temperatures for the Earth's average surface temperature have been derived, with a best estimate of roughly 14°C, i.e. 57.2°F. However, the correct temperature could easily be anywhere between 56 and 58°F, and uncertainty increases at smaller (non-global) scales.
(existing section) Temperature processing software
In September 2007, ..."
Enescot (talk) 04:36, 28 December 2012 (UTC)

Subsurface ocean temps[edit]

This article erroneously defines the ITR as being only about surface temp. That's false, but I don't enough about the subsurface instrumental record to write good text. Help please? — Preceding unsigned comment added by NewsAndEventsGuy (talkcontribs)

Um. Initially the instrumental temperature record only documented land and sea surface temperature, but in recent decades instruments have also begun recording sub-surface ocean temperature is too simplistic. People have been documenting sub-sfc temperatures for ages. The correct sequence is land-sfc before the others, then ocean sfc thinly, with sub-sfc coming in slowly. The difference in recent decades is in volume of coverage, ie quantitative, not qualitative William M. Connolley (talk) 12:54, 28 January 2014 (UTC)
I'd welcome your expertise revising the text to include subsurface! You say "ages", and I don't know...I'm a layman. But I can read, and in Mann & Krump's "Dire Predictions", in the glossary, it says the land surf record is 150 years, and ocean subsurface record goes back only 5-6 decades. If that's "ages" for subsurface then I guess I agree. How would you phrase it better? And please do! NewsAndEventsGuy (talk) 13:09, 28 January 2014 (UTC)